Suppose you have a frictionless road. We'll assume this for simplicity. Then on a flat frictionless road the car will just go in straight line. You can't drive in a circle. OK so far?
Now if you bank the road this creates a radial force inwards towards the centre of the circle. So this will accelerate the car inwards and the car will move in a curve rather than a straight line.
If the banking angle is small the inwards force is small and although the car move in a curve its trajectory is only slightly curved so it still moves away from the centre of the circle.
